Method of casting wax slabs



y 4, 1954 H. JENNINGS METHOD OF CASTING WAX SLABS Filed Nov. 5, 1951 m Ui E m Fall}? n m N i I I I l l WWW Qt" L INVENTOR.

Mon 15. JIM/1m .5 BY 2 7 Patented May 4, 1954 STATES} ENT OFFICE METHOD0F" GASTING' 'WAX SIiABS Leon. H. Jennings; Beaumont-flex, assign'on to:Socony-Vacuum Oil Company Incorporated,- New York, N; Y'., a.corporation 01 New- York. ApplicationeNoveinlier 3, 1951 serial Nor-254,682

This: invention is. directed. to. amethod: for the. ,1

production of para fiin; waxes inslab form.

On'exnorma-l form in which parafiin wax is-prepared for distribtution tothe trade-is in a. slab, or cake-weighing about eleven pounds, Whichisabout 1 8 inches. by 11 inches and: about 1 /2. inches thick.

Usually these oakesor slabs are prepared by a batch method, using anarrangementof: alternating opens-top molds and internally water-- cooleddividers which are assembled. upon. siderods and held together byend-pressure on. the assembly. The melted. wax is poured; into thetrough formed by the top of the assembly and.

fills. the mold. and is cooled therein by waterpassed through thedividers. After cooling, the

waxremaining above the top of the moldsis out: or scraped oif, the.assembly isloosened andthe,

cakes are removed. Thismethod. involves avery considerable amount ofhand-labor and handling of cakes. i

There has now been applied to: this problem a process of continuousmolding: in pans adapted from a. somewhat analogous industry.

The object of this invention is to; provide: a.

proper control for this operation, as will be ex- Dlained in detailherein.

In order to understa-nd the operatiomreferenee is now made-to thedrawing which accompanies; and is-made a. part of this specification.Iihis; drawing shows, in highly diagrammatic. form;

the process of slab casting. A seriesof'. pans I, I 1, etc, are carried.upon-a chain 2, 2, 2, etc;

Thesepansare. of the proper size for-the desired: wax slabs, andarecloselyspacedzuponthesidei chains and arranged in transversesgangs ofsix pans, side by side. At the left hand end of the lowesnpass. off-thechaimpthe'ypa's's under a depositor, consisting .of a hoppers and. atransverse series of piston type feeders 4, whereby a measu'red'arnountof moltenwax is withdrawn from hopper 3 and deposited in each pan.Passing to the right, the-pans enter into'a cooled:,en=- closuredesignated by dottedlines I 5, wherein'they' 5 Claims. (01. ital-58)one-side; or. the: cooler: enclosure: andzblown transversely.therethroughi.

Emerging from. the cooler: 5,:Iat hand endin. the: diagram; the pans arepassed throughanz upsetting turnand putinto-an upside down; position inthe: chain. passindicated by 6..

This upsettingresultsin the dropping-of the wax:-

slab- 1 which throughthe agency of'conveyors. 8i

and 9, associated with the upsetting;orjdischarger;

mechanism, is finally placed: inposition: on discharge conveyor H bywhich; itis withdrawn laterally from; the slab-hing machine;

temperature and airrate'in the cooling: chamber and to vary the rateofcooling when necessary by varying the conveyor.- speed and; hencetheyresidence time of the pans; within the.v cooling. chamber; a

This. equipment. is' essentially the" same an is Y usedinvslabbingcc'hocoi'ate,;etc;, and. as such forms.

no part of this invention.

The present requirements for cake. wax, particuiarly paraffin requirecareful attention to appearance. The surface of the cake must 'beiclean.

and free from ripples and bumps and the cake should show nolaminationnor broken edges. Even more: important, its surfaces should be cleanlyformed and as nearly as possible at right angles to each other foreconomy and ease in packaging. This last requires that. the pans be 7formed with. a veryminimumof taper or draft? and giv s rise to a problemin cleanly dumping" the pans; These and other -considerations make itnecessary-to closely control the operation as to 'temperat'urea First,as some loading- 0f the pans. Obviously this temperature should" beiicarto the melting point ofthe wax tosave cooling load; I-tcannot be toolow. If toolow, it is' found that films of cooler wax-dorm next to thebottom and sides or thep'an, the cakerefuses to dumpcleanly regardi'essof -final temperature; and also trouble is had with cake lamination,frequently causing scaling of the discharged cake.

I have found that the proper temperature at which the wax, regardless ofits melting point, must be loaded to the pan is at 20 F. above its ASTMmelting point. (ASTM melting point is the melting point as determined byASTM Method D8'7-42, specified by the American Society for TestingMaterials, also designated as ASA Method No. Z 11.4-1942 and API No.513-42.)

the upper. left The pans I are then righted. and prior. to: loading. bydis.-

Th temperature of loading should not vary more than minus 2 F. from thespecified level.

The final temperature to which the wax should be cooled is also a matterof major importance. It should not only be low enough to permit cleandumping of the wax cake or slab, but since the slab is cooled from theoutside and the center of the cake is warmest, the cake or slab shouldnot contain enough residual heat to soften up and lose shape or block(adhere to adjacent slabs), after removal from the pans. I have foundthat this condition can be fulfilled by cooling the cake until itscenter temperature is at least about 30 F. below the ASTM melting point.This temperature can be taken by inserting thermometers from time totime in individual cakes as a check, but in actual operating practise ishandled by holding the temperature and rate of cooling air flow constantand controlling the length of time of exposure of the slabs to thiscooling.

The rate' of cooling is also of importance. Shock chilling is not afactor since 'I have found that the air maybe as cold as practicable,even 5 F., so long as even air flow and exposure of the slabs thereto isprovided. In some instances it may be necessary to protect a portion ofthe cooling cycle, such as the portion found at the lower right hand endof the diagram, from too vigorous air flow. The object is to secure auniform rate of cooling throughout the entire chain pass. With suchuniform cooling, although the center of the slab will of course coolmore slowly than the outside, fairly uniform conditions within the slabwill be gotten if the time of cooling is proper. This of course dependsnot so much upon the temperature of the cooling air as it does upon thenature of the Wax itself as a heat transfer medium. I have found thatfor wax slabs of conventional size, cooled from at least F. above theirASTM melting point to at least 30 F. below their ASTM melting point, thetime of cooling should be of the order of 135 to 150 minutes. Expressedin rate, the cooling should be from not less than about 2 minutes perdegree F. to not more than about 3.5 minutes per degree F.

Several examples of successful operation are as follows:

In these operations, clean, sharply formed paraffin wax slabs, withoutinternal laminations and without broken edges, pickouts, or otherevidence of poor dumping were made, and dumped with ease.

Neither did the slabs so made show any evidence of blocking ordeformation after which were not marketable because of the variousdefects mentioned.

I claim:

1. In the method of converting paraffin wax into clean, sharply-formedparaffin wax slabs, substantially without internal laminations andbroken edges, which includes depositing parafiin wax in a mold pan,moving the pan through a cooling chamber and discharging a solidifiedwax slab from the pan, the improvement, which comprises loading the waxinto the pan at a temperature not less than about 20 F. above its ASTMmelting point, cooling the wax slowly to a temperature at the center ofthe slab which is not above about 30 F. below the ASTM melting point ofthe wax, and dumping the slab.

2. In the method of converting paraffin wax into clean, sharply-formedparaffin wax slabs, substantially without internal laminations andbroken edges, which includes depositing paraffin wax in a mold pan,moving the pan through a cooling chamber and discharging a solidifiedwax slab from the pan, the improvement which comprises loading thewaxinto the pan at a temperature not less than about 20 F. above itsASTM melting point, cooling the wax slowly during a time of from aboutto about minutes to a temperature at the center of the slab which isnot, above about 30 F. below the ASTM melting point of the wax, anddumping the slab.

3. In the method of converting parafiin wax into clean, sharply-formedparailin Wax slabs, substantially without internal lamination and brokenedges, which includes depositing paraffin wax in a mold pan, moving thepan through a cooling chamber and discharging a solidified wax slab fromthe pan, the improvement which comprises loading the wax into the pan ata tempera ture not less than about 2 0 F. above its ASTM melting point,cooling the wax slowly at a rate ranging from not less than about 2minutes per degree F. to not more than about 3.5 minutes per degree F.to a temperature at the center of the slab which is not above about 30F. below the ASTM melting point of the wax, and dumping the slab.

4. A method as defined in claim 1 wherein a chain of mold pans areconveyed continuously chain-0f mold pans are conveyed continuouslythrough the wax depositing station, thence through the cooling chamberand thence through the slab dumping station. 7

References Cited in the file of this patent UNITED STATES PATENTS

1. IN THE METHOD OF CONVERTING PARAFFIN WAX INTO CLEAN, SHARPLY-FORMEDPARAFFIN WAX SLABS, SUBSTANTIALLY WITHOUT INTERNAL LAMINATIONS ANDBROKEN EDGES, WHICH INCLUDES DEPOSITING PARAFFIN WAX IN A MOLD PAN,MOVING THE PAN THROUGH A COOLING CHAMBER AND DISCHARGING A SOLIDIFIEDWAX SLAB FROM THE PAN, THE IMPROVEMENT WHICH COMPRISES LOADING THE WAXINTO THE PAN AT A TEMPERA-